1. Field of Invention
The present invention relates to a power distributor to be mounted on a vehicle, and a method for producing the power distributor.
2. Description of Related Art
An electric connection box or the like having fuses and relay switches incorporated in a power distribution circuit constituted by a laminate of a plurality of bus bar boards is generally known as a power distributor for distributing electric power given from an on-vehicle power supply into a plurality of on-vehicle loads.
In order to achieve reduction in size of the electric connection box and highspeed switching control, development of a power distributor using semiconductor switching devices such as FETs, instead of the aforementioned relay switches, interposed between input and output terminals has been further advanced in recent years. For example, JP-A-10126963 discloses a power distributor using a plurality of semiconductor switching devices having drain terminals which are connected to a metal plate connected in turn to a power supply input terminal, source terminals connected to power supply output terminals respectively and gate terminals connected to a control circuit board.
The power distributor disclosed in JP-A-10-126963 is superior to the background-art electric connection box in that reduction in size is advanced by introduction of semiconductor switching devices. The power distributor disclosed in JP-A-10-126963, however, must have an input terminal for introducing a large current and a large number of output terminals for distributing electric power into electronic units and must further have a control circuit board for controlling the semiconductor switching devices. Hence, it is difficult to reduce the size greatly. Particularly there is a large problem in reduction in thickness.
When the power distributor is to be mounted on a vehicle, there is another important problem to be solved. That is, the state of connection between each semiconductor switching device and the metal plate can be held steadily by a simple structure so that vibration at the time of running of the vehicle does not easily cause disconnection of each semiconductor switching device from the metal plate.
On the other hand, in production process, there is a possibility that a resin housing may be partially melted by heat due to soldering or the like performed for mounting the semiconductor switching devices on the metal plate after the metal plate constituting a power distribution circuit is incorporated in the resin housing. In order to avoid such melting of the housing, if the metal plate is incorporated in the housing after the semiconductor switching devices are mounted on the metal plate, the work of incorporating the metal plate in the housing is difficult. Hence, in any case, the assembling work is not easy and the mass-production characteristic is poor.
The present invention is devised upon such circumstances and an object of the invention is to provide a vehicle power distributor in which good power distribution on a vehicle can be performed in a simple and thin structure, and to provide a method of producing the power distributor by simple steps.
In order to solve the above problems, according to the present invention, there is provided a method of producing a vehicle power distributor which is to be mounted on a vehicle for distributing electric power from a common power supply into a plurality of electric loads and which uses semiconductor switching devices interposed between the power supply and the loads for switching on/off current conduction thereof, comprising the steps of: forming a bus bar aggregation containing an input terminal portion connected to the power supply, a device mount portion connected to the input terminal portion and having the semiconductor switching devices mounted on the device mount portion in the condition that a power supply side current-conduction terminal of each semiconductor switching device is connected to the device mount portion, and a plurality of output terminal portions to which load side current-conduction terminals of the semiconductor switching devices are connected respectively, the input terminal, the device mount portions and the output terminal portions being integrated with one another; mounting the semiconductor switching devices on the device mount portion by connecting power supply side current-conduction terminals of the semiconductor switching devices to the device mount portion of the bus bar aggregation and connecting the load side current-conduction terminals of the semiconductor switching devices to the output terminal portions respectively; molding a housing from an electrically insulating material around the device-containing bus bar aggregation produced by the mounting step so that at least the input terminal portion and the output terminal portions are partially exposed; and cutting joint portions between a plurality of terminal portions inclusive of the input terminal portion and the output terminal portions after the molding step (Aspect 1).
Further, according to the present invention, there is provided a vehicle power distributor which is to be mounted on a vehicle for distributing electric power from a common power supply into a plurality of electric loads and which uses semiconductor switching devices interposed between the power supply and the loads for switching on/off current conduction thereof, comprising: a bus bar aggregation including an input terminal portion connected to the power supply, a device mount portion connected to the input terminal portion and having the semiconductor switching devices mounted on the device mount portion in the condition that power supply side current-conduction terminals of the semiconductor switching devices are connected to the device mount portion, and a plurality of output terminal portions to which load side current-conduction terminals of the semiconductor switching devices are connected; and a housing molded from an electrically insulating material around the device-containing bus bar aggregation so that at least the input terminal portion and the output terminal portions are partially exposed in the condition that the plurality of semiconductor switching devices are mounted on the device mount portion of the bus bar aggregation (Aspect 5).
Because the power distributor according to the present invention has a structure in which semiconductor switching devices are mounted on a bus bar aggregation constituted by a single metal plate and in which a housing is molded around the bus bar aggregation provided with the semiconductor switching devices, this power distributor is smaller in size and thickness than the background-art power distributor and the state of connection between the bus bar aggregation and each semiconductor switching device is held steadily by the housing molded around the bus bar aggregation provided with the semiconductor switching devices. Moreover, the power distributor can be produced by the simple steps of: mounting the semiconductor switching devices on the bus bar aggregation; molding the housing around the bus bar aggregation provided with the semiconductor switching devices; and cutting off suitable conductor portions.
The step of forming the bus bar aggregation can be performed, for example, by punching out the bus bar aggregation from a single metal plate (Aspect 2) so that massproduction characteristic can be more improved.
Further, a heat-radiating member is attached to the housing formed by the molding step so that the heat-radiating member is exposed to the outside of the housing in a state in which heat can be transmitted between the heat-radiating member and the device mount portion (Aspect 3 or 6). Accordingly, heat generated from the semiconductor switching devices partly or wholly embedded in the housing can be effectively released to the outside of the housing.
Further, if a window through which joint portions between the plurality of terminal portions are exposed is formed in the housing in the molding step, and the joint portions are cut off through the window in the cutting step (Aspect 4), the joint portions can be cut off easily without any inconvenience after the molding step even in the case where the joint portions are provided, for example, in intermediate portions of the bus bar aggregation.
Further, according to the present invention, there is provided a bus bar aggregation for forming a vehicle power distributor which is to be mounted on a vehicle for distributing electric power from a common power supply into a plurality of electric loads and which uses semiconductor switching devices interposed between the power supply and the loads for switching on/off current conduction thereof, comprising: an input terminal portion connected to the power supply; a device mount portion connected to the input terminal portion and having the semiconductor switching devices mounted on the device mount portion in the condition that power supply side current-conduction terminals of the semiconductor switching devices are connected to the device mount portion; and a plurality of output terminal portions to which load side current-conduction terminals of the semiconductor switching devices are connected, wherein the bus bar aggregation is made from a single metal plate, and wherein the input terminal portion, the device mount portion and the output terminal portions are integrated with one another (Aspect 7).
If the bus bar aggregation is used, it is possible to easily produce a devicecontaining bus bar aggregation for a power distributor, wherein the plurality of semiconductor switching devices are mounted on the device mount portion, the power supply side current-conduction terminals of the semiconductor switching devices are connected to the device mount portion, and the load side current-conduction terminals of the semiconductor switching devices are connected to the output terminal portions respectively (Aspect 9). According to the bus bar aggregation provided with the devices, the aforementioned small-size thin power distributor can be obtained by the simple steps of: molding the housing around the bus bar aggregation; and cutting off suitable portions.
Here, the shape and arrangement of each portion in the bus bar aggregation can be set suitably. For example, preferably, the configuration is made so that the device mount portion extends in a direction of the arrangement of the semiconductor switching devices, the input terminal portion and the output terminal portions extend in a direction approximately perpendicular to the direction of the length of the device mount portion and are arranged at intervals in a direction approximately parallel with the direction of the length of the device mount portion, and end portions of the input terminal portion and output terminal portions opposite to the device mount portion are connected to one another by a connection belt extending approximately in parallel with the device mount portion. According to this configuration, the respective portions can be integrated with one another in a compact layout in which the device mount portion and the connection belt are disposed in lengthwise opposite sides of the input terminal portion and output terminal portions arranged unidirectionally.